op minneapolis



v Jan. 1, 1929.

R. 17,180 C. T. HIBBARD METHOD AND MEANS FOR STARTING SYNCHRONOUS MOTORS Original Filed Jan. 17 1 0 J9 w 4/] I 38 .37 Y 9 2a a4 1 j K mag J3 2.9

. .35 I JJL 0 6 I o w 3 m0 INVENTOR ATTORNEY Reissued Jan.'1,192 9. V Re. 17,180

UNITED STATES PATENT OFFICE.

CHARLES TRUMAN HIBBARD, OF MINNEAPOLIS, MINNESOTA, ASSIGNOB,'BY MESNE ASSIGNMENTS, TO ELECTRIC MACHINERY MFG COMPANY, OF MINNEAPOLIS, MINNESOTA, A CORPORATION OF MINNESOTA.

METHOD AND MEANS FOR STARTING SYNCHBONOUS MOTORS.

Original K051340322, dated August 23,1927, Serial No. 852,159, filed January 17, 1920. Application for reissue filed November s, 1928. Serial N 315,059.

One object of my invention is to provide a riod required for the motor to attain synchromethod and means for starting synchronous nous speed. motors from the -actuation of a push button. Inasmuch as the time required for the mo- Another'object is to provide a method'and tor to attain synchronous speed Will vary 55 means whereby the motor is started automatiunder load conditions, it is evident that no cally at a reduced voltage and with no excitepr e ed n v ca be u ed fo either tion current, and whereby when the motor has applying the full Volta e to the motor, or attained a predetermined percentage of synmore especially, for appdying the excitation chronous speed, the full voltage will be apcurrent at the right instant. 3 1o plied, to the motor, and thereafter the field It is also apparent that if the field is of the will be automatically excited. wrong polarity when the field circuit is closed Another object is to provide improved there will be a surge in the linecurrent and means and method for automatically exciting the motor will also be subjected to heavy th motor field as the motor approaches synmechanical strains, so the proposition that 55 chronism'. a v the field circuit is closed will be accepted by Another object is to provide a method and everyone skilled in theart. means whereby the field will possess the cor- So far as I 1 e, there have been no rect polarity when the field circuit is closed,' feasible, auton'latic'means proposed for auto- VVitl' these and incidental objects in view, matically starting a synchronous motor to 70 2 the invention consists of certain novel feameetthe necessary requirements, and to the tures of construct-ion and combination of best of lny knowledge, no practical means parts, the essential elements of which are WlHLtGVBIllEI-S been suggested'for automaticalhereinafter described with reference to the lY securing the correct-polarity at the instant drawing which accompanies and forms a {he fi is l S 75' part of this'speeification. When the voltage from the low tap of the In the drawing, Figure 1 i a s h atic transformer is thrown onto the motor 3, ourview of a circuit showing one embodiment of rent is induced in the field winding and this my invention; and Figure 2 is a conventional current is maintained when the-full voltage representation of an oscillogram showing the is applied and continues at substantially its 30 current induced in the field winding as the full value until the motor is within a fewper 'motor is started. l cent of synchronous speed. c

In the ordinary method for starting syn- This field current is,of course, alternating, chronous motors it is customary to throw a and like the field voltage, has a frequency switch which will connect the motor with a equal to theslip, decreasing from a maximum 35 t-ap from the, transformer so as to start the frequency equal to that of the supply current, motor at a reduced voltage and with no excitauntil it reaches zero when the motor is in syntion. l chronism. 7 -When the motor has attained-a. certain As shown in the oscillogram in Figure 2, 1 speed a 'switch is thrown so as to bring a full. when the motor is first started the current has 90 I 0 voltage on the motor and then when the moa frequency at the point- 1 equal to that of the tor has'practically reached synchronism, the supply current; at the point 2 the frequency field is closed and the motor pulls into synhas decreased greatly, while at the point3 the chronism. frequency is extremely slow, and from the One ofthe problems of the handling of point 4 to the point 5 the current dies away 95 synchronous motors. and especially by unand at the point 5 it'is zero,this representing skilled h'elp,has been to devise means whereby the instant at which the motor reaches synthe full voltage willbe thrown onto the motor chronism. at the proper time, and another still more In my method I utilize this induced field important problem has been to devise means current to determine, first, the point at which 10 whereby the field excitation current may be the full line voltage should be thrown onto thrown on at the proper time during the pe the motor; second, to determine positively into synchronism.

the point at which the excitation current I of the motor the instant at which the field cur rent should be applied,'it is nevertheless true that in this induced field current we have a means at hand which indicates in itselfthe time at which the field eicitation current thepointl' l 6 should be ap lied, and, also the time of the cycle at which the application-must be made in order that the excitation will be in the proper direction to'cause the motor to .pull

. Obviousl this inducedfield current also furnishes t e best ossible means for determinin at what instant the full voltage shoul "be applied to the motor as the field current is at all times in definite timed relation with,the speed ofthe motorand the frequency of the supply current.

Inasmuch as the frequencies at the point 2 Figure 2, is greatly reduced below that at t e int 1, it is evident that electrical means can e devised that will operate at frequencies such as that representedat point 2, and will not operate at frequencies such as that re resented at the point 1.

t is also evident that there is a sufiicient. difierence in frequencies between the points 2 and 3 to allow the use of an electricaldevice that can be adjusted to function in a certain way under influence of frequencies such-as that represented at 3 and not to func tion in the samemanner under .influence of frequencies 'such as that represented at ,the

point 2.

It is also obvious that an electrical device can becojnstructed that will actuate for instance, when'this current is above the line, as at 6, but will not actuate when the current 3 is below the line, asat 7, so' that the device actuated by the electrical condition of frequencies and direction of] pulsation, will necessarily a ply the full 170 tageat the proper time, of the'field current atthe proper time to lift the motor into regard to the length of time that has elapsed from the point 1 to the point 2, at which point the full volt e might be a lied; or from oint 3, at w 1ch time application of the fi d excitation current mi'ght made. a In other words, either the application of thd full voltage or theapplication of the fieldv excitation current,or' both, maybe madeto depend absolutely and, entirely upon the internal electrical condition of the field winding itself, through the action of this induced current.

'In the. circuit shown in Figure 1, I have indicated one means by which this may be ac- -ing the attention mote point, such for instance as a float switch chronism, and without.

,contact 57 of the push button complished and in this circuitthe powerlines are represented at 8 with the usual trans,

former 9 and ammeter 10.

In starting the motor the attendant has only to close the circuit by means of the push button 11 and the motor 1s brought into synchronism in the proper manner, automati-- cally and without furtherattention or care buttoncircuit. The push button 11 may be actuated by an automatic device not requir of the operator and at a rein a watertank or a pressure gauge on a gas tank. Y

The operation of the push button 11 actu-' ates a relay or contactor switch 12,,thecircult being as follows: Source of current supply 13, wire 14, push button 11, wire 15, wind ing 16, and wire 17 to the other side of the source of current sup 1 Upon the closin o the contact 18 a switch 19 is thrown to t e right, as shown in, the sketch, by the actuation of the coil 20, circuit being as follows: Power wire 21, wire 22, contact 18, wire 23, coil 20, wire 24, to power wire 25.

The switch, when thrown to the right, remains in that the coil 20 is energized only so long as the contact18 remains closed The closing of the switch to the right up lies a full voltage of the line to the transormer' 26, the circuit being as follows: Power lines 25, 21 and 27 switch 19, wires 28, 29 and 30, to the transformer 26.

From the low.volta e taps the current is applied to the motor, the circuit being as follows: Wires 31,32, 33, wires 34,35, 36, to the stator 37 of the motor, a As soon as the current is ap lied to the stator current is induced in t e rotor 38 through the followin circuit: Rotor 38,

position until withdrawn, but

wire 39, primary 40 o the transformer 41,

wire 42, eld rheostat 43, wire 44, contact 45 of the 'switch 46, field discharge resistance 47,

When the motor is first sup lied with the current a circuit is establishe through the actuatlng coil 53 of the switch 19, the circuit being as follows: Wire 35, wire 54, coil 53,

throu' h the frame of the relay 60 an wire 61 to the wire 34.

While the coil 53 is energized, at least partially, by this circuit, the switch 19 is not 41', contact thrown to the left by the actuationfof thecoil' 53 as the contact 60 in the circuit; energizing the coil 53 is broken by .the energizing of the coil 40' before the coil 53 can affect the position of the switch 19. The relay41 is 58, wire 59, t

ill

energized by "the current from the trans? former 41 as the secondary 43 is directly connected to the winding of the relay 41 The frequency relay 41' isv ad'ustable and is set to release its armature w en the frequency of its actuating current falls below a gfedeterminedamount, for instance, that in- 'cated at point 2, Fi ure 2, the relay being such that it will quic y respond to a frequency-such as that indicated at 1, Figure 2, and release under the lower frequency as in dicated. A

It is evident therefor, that when the motor has reached a certain predetermined percentage of synchronism such that the induced current in thefield winding would have a frequency such'as is represented at 2, Figure .2, the frequency rela 41 will be released and the contact clos and this contact 60 will remain closed under decreasing frequencies. Upon the closing of the contact 60 the 'coil 53 is energized and the switch 19 thrown to the left, thus applying full voltage to the motor through the overload relays 100. g

In the field circuit already traced is included the primary 50 of the transformer 51 and the secondary 62 of this transformer is connected directly to the winding 63'of the frequency rela 64, which is adjustable and is so adjusted t at it will be actuated by a current of frequencies higher than that represented at the point 2, Figure 2, for'instance,

and will release at a frequency such as that represented at 3, Figure 2.

The fre uency relay 51 was actuated and its armature rawn up and contact 65 opened at the same instant that frequency .relay 41' was actuated,'and when its armature is released as the motor approaches synchronism and at such a point that the frequency of the 7 induced field windingris represented at 3, Figure 2, a circuit is established as follows: field winding 38, wire 52 primary, winding 50 of the transformer 51, wire 49, wire 66', frame of the relay 64, contact 65, wire 66, winding 67 of the polarized relay 68, wire 69, wire 44, rheostat 43, wire 42, primary winding 40' of the transformer 41 and wire 39 back to the field winding 38. 7

, Inasmuch as the relay 68 is polarized preferably by a permanent magnet, it is evident it will respond to pulsations of cur rent of one direct-ion only and the contact 7 0 will be closed only when the polaritybf the current passing through the relay is of proper sign such, for instance, as that at 6, Figure 2, and that the contact 70 will be opened when the current is of the opposite polarity, as at 7, Figure 2. V

The closing of the contact 70 energizes the coil 71, the circuit being as follows r source of field excitation current at 72, wire 73, Wire 74, coil 71,, wire 75, armature 76 of the relay 68, contact 70, wire 77, wire 78, to the other side of'the source of current supply.

The energizing of the coil 71 throws the switch 46 to the r1 ht, applying the field current to the field winding 38 and cuttin' out the field discharge resistance 47, the fiel excitation current' circuit being as follows: source of current supply 72, wire 73, switch 46, wire 48, wire 49,fiprimary 50 of the transformer '51, wire 52, eld winding 38, wire 39, primary 40 of the transformer 41, wire 42, rheostat 43, wire 44, switch '46, wires 7 8, 7 8, tq the other side of the source of current sup- P is explained above, the field circuit includes the primary 40 of the transformer41 and the primary 50 of the transformer 51. These primary transformer windin constitute a reactance connected in the fie d circuit at all time. The secondary winding 43' of transformer 41 and the secondary winding 62 of transformer 51 constitute a reactance which may be said to be included in the field circuit whenthe field circuit carries an alternating current, for in this event a currentinduced' from the prima? transformer windings in the field circuit ows through the secondary windings of these transformers. In

like manner-the rela s 41 and 64 may be regarded as included 1n the field circuit when the field winding carries an alternating current.

Inasmuch as the field was excited by. means of the magnetizing switch at a predetermined condition of the cycle of the induced field my method.

The polarized relay is shown in the drawing as a conventional representation of a polarized relay and the magnetically operatcd switches are shown as conventional representations of switches whose operation is well known to all those skilled in the art, and While shownconventionally, I wish it understood that they represent operative devices, as I will claim under this patent not only the method otstarting synchronous motor-s but also the means for so doing, said means being a new combination of well known devices producing a new effect. As stated above, the frequency relay 64 is adapted to open the contact 65 when the frequency of the induced field current is higher than that represented at the point 2, Fig. 2,for instance, and to close this contact when the frequency is such as that represented at 3, Fig. 2. Therefore,

if the motor pulls out of step for an reason and the frequency of the induced eld current increases beyond the point 2, Fig. 2, for instance, the relay 64 will operate to break the circuit including coil 71 of the field switch 46, thus permitting this switch to open and to be understood frequency relay thereby disconnect the field winding from the source of excitation current.

Under ordinary conditions I would so adjust the frequency relay 41' as to impress the full voltage on the motor when approximately seventy per cent of synchronous speed has been attained, and so time or adjust the (ii that the field would be closed at approximately ninety per cent of synchronous speed. 7

One of the main benefits of my system, however, is that the adjustments may be made on the relays to meet the operating con ditions of any particular mot-or, so that when the motor is started by the pressing of the push button 11 the motor will be brought up to synchronism under the best possible conditions for that motor for the particular load which it is handling.

The winding of the frequency relay 64 is energized by the secondary current of transformer 51 so the action of closing the ma netic gap when the armature of the relay is rawn up will choke the secondary current-and thereby make the armature more easily released when the frequency of the induced current in the field winding falls below the point 2.

While from the nature of the method and means disclosed it is evident that the operation will be'positive in nature, yet, if for anyreason the frequency relay 64 failed to operate between the points 3 and 5, it would necessarily operate at the point 5, as there would be no induced current whatever in the field winding at that time; hence the polarized relay 68 would, in any event, be actuated so that even in case of failure of operation of the frequency relay the field current would be thrown in.

The push button 58 may be located at a distant point from the motor and there may be a number of such buttons with their contacts in parallel, so that the coil 53 and the switch 19 would be energized-upon actuating any one of these push buttons. This would allow the throw-out springs 53' toopen the switch 19, thus disconnecting the motor from the line.

I have described my invention as applied to a polyphase synchronous motor but it will be understood that the invention can be used to good advantage with synchronous machines of various types such as rotary con verters and alternatorsQ While I have described my invention as including means for applying full voltage and subsequently closing1 the field circuit, yet it is t at my invention can be applied to synchronous machines where it synchronousspeed.

is desired to close the field circuit prior to the application of the fu1l voltage to the armature winding.

While I have shown one style offrequency relay and one style of polarized relay and acertain conventional clrcuit, it is apparent that this invention covers broadly any method or means controlling any part or all of the starting of a synchronous motor through a means controlled by the internal electrical condition of the field winding, and covers broadly any method or means by which the right polarity may be secured at the instant the field is closed.

The overload relays 160 are connected in so the supply circuit in such a manner that the line current does notpass through these relays during the period when reduced voltage is impressed on the motor. armature. This arrangement prevents the overload relays so from operating during the first part of the starting period when the line current is excessive. 3

While this invention has been described as applied to its use with a synchronous motorou of the type which is started by first applying reduced voltage, yet the motor starting sys-' tem may be applied to synchronous motors of the full. voltage type, i. e. synchronous motors which may be started by impressing line 95 voltage directly on the armature.

I claim:

1. In a system of the type described, the combination with a motor having a field winding, of a source of excitation for the field winding, automatic means responsive to the electrical condition of the field winding for supplying excitation current to the field winding of the motor when it has'reached a predetermined speed, said means being adapted to open the field circuit when the motor speed falls below a predetermined speed.

2. In a system of the type described, the combination with a motor having a field windwinding, winding to the source of excitation, and means responsive to the electrical condition of the field winding for closing said switch when the of a source of excitation for the field a switch for connecting the field motor speed increases to a predetermined value and for opening said switch when the motor speed falls below a certain speed near I 3. In a system of the type described, the

combination with a motor having a field wind- 12o ing and an armature winding, of means for applying voltage to the armature winding, a switch for connecting the field winding of the motor to a source of excitation current, and

means responsive to the electrical condition of the main field winding for closing said switch when the motor speed increases to a predetermined value and for openi said switch when the motor falls be ow a. co 'n value.

- combination with a motor 4. In a system of the type described, the combination with a motorhaving an armature winding and a field winding, of means for apsaid automatic means being adapted to open the field circuit when the motor speed falls below a predetermined value. 1

5. In a system of the type described, the

aving an armature and field windin of a source of excitation for the field winding, means for applying voltage to the armature of the motor, an automatic means associated with the'motor for supplying excitation current to the field wind ing when the motor has reached a predetermined speed and for opening the fie d circuit when the motor speed falls belowa certain value, said automatic means being exclusively responsive to the slip frequency of the current induced in the main field winding of the motor.

6. In a systemof the type described, the combination with a motor having a secondary winding, of a source of direct current, a resistance, means arranged toshort circuit the secondary Winding t rough said resistance when the motor is startin a switch for connecting said winding to t e source of direct current, and means responsiveto the electrical condition of said winding for simultaneously opening the short circuit through said resistance and closing said switch when the motor has reached a predetermined speed and for opening said switch when the motor speed falls below a certain speed. 7

7. In a system of the type described, the combination with a motor aving an'armature winding and 'a field winding, of means for applying voltage to the armature winding, a source of direct current, a resistance, means arranged to short circuit the field winding of the motor thru said resistance when the motor is started, a switch'for connectingsaid winding to the source of'direct combination with a motor current, and means responsive to the electrical condition of said field winding for simultaneously opening the short circuit thru said resistance and closing said switch when the motor has reached a predetermined speed'and for opening said switch when the motor speed falls below a certain value.

8. In a system of the ty e described, the

aving an armature winding and a field winding, of means for applying voltage to the armature winding, a source of direct current, a resistance, a two-position switch arranged so that in one position it connects said resistance across the field winding and in the other position it connects the source of direct current to the field winding, and means responsive to the electrical condition of said field winding for operatin said switch to disconnect said resistance rom the field winding and to connect the source of direct current to the field windin when the motor has reached a predeter mlned speed.

9. In a system of the type described, the combination with a motor aving an armature winding and a field winding, of means for applying voltage to the armature wind mg, a source of direct current, a resistance, a two-position switch arranged so that in one position it connects said resistance across the field winding and in the other position it connects the source of direct current to the-field winding, and means responsive to the electrical condition of said'field winding for operating said switch to disconnect said resistance from the field winding to connect the source of direct current to the field winding when the motor has reached a predetermined speed, and to disconnect the source of direct current from the field winding and connect the resistance thereto when the motor speed falls below a certain value.

10. In means for starting a synchronous motor thecombination with the field winding of said motor, of a frequency relay, a polarized relay, and a source of field excitation current, and "an electrical circuit connecting said devices whereby current may be supplied to said field winding when the frequency of the induced current therein is below a certain value and the cycle thereof is of a certain direction of pulsation.

11. In a system of the ty described, the combination with a motor ture and a field winding, ofa source of excitation for "the field winding, means for applying voltage to the armature of the motor, and,

automatic means associated with the motor for supplying excitation current to the field winding when the motor has reached a-predetermined speed, said automatic means comprising a field switch and apolarized freuency relay responsive to the frequen of t e induced current in the main field wmding, said relay being connected in circuit with said field winding at all times.

12. In'a system of the type described, the combination with a, motor having a field winding and an armature winding, of means for applying. voltage to the armature winding, and automatic means associated with the motor for supplying excitation current to the field windin when the motor has reached a predetermine speed, said automatic means comprising a field switch and a polarized freuency relay responsive to the frequency of t 0 induced current in the main field winding, said relay being in operative connection with said field windin at all times. 13. In a system of t e type describedrthe combination with a motor having an armature winding and a field winding, of means aving an armaexcitation current to the field windin mg 0011 connecte for applying voltage to the armature of the motor, and automatic means responsive to the electrical condition of the field Winding for supplying excitation current to the field winding when the motor has reached a predetermined said automatic means beigg inopera 1e until voltage has been appli to the armature, and said automatic means being adapted to open the field circuit when the motor speed falls below a predetermined. value.

14. In a system of the type described, the combination with a motor having an armature and a field winding, of a source of excitation for the field winding, means including a switch for applying voltage to the armature of the motor, and automatic means responsive to the electrical condition of the field winding for supplying excitation current to the field windin of the motor when the motor has reach a predetermined s eed, said automatic means being inopera le until volta has been applied to the armature, and said automatic means being adapted to open the field circuit when the motor speed falls below the predetermined speed.

15. In a system of the type described, the combination with a motor aving an armature winding and a field winding, of means for applying voltage to the armature of the 'motor, said means including aswitch controlled circuit and an electromagnetic switch having a coil energized by said circuit, and automatic means res nsive to the-electrical condition of the fiel winding for supplying when the motor has reached a predetermine speed, said automatic means being inoperable until voltage has been applied to the armature, and said automatic means being adapted to open the field circuit when the motor speed falls below a predetermined value.

16. In a system of the type described, the combination with a motor having a field winding of a reactance connected in the field circuit, a frequenc relay having a magnetizd across the reactance, and a field switch adapted to be closed by said relay when the uency of the induced current in the field winding has decreased to a predetermined value, the reactance being connected in said field circuit at all times.

17. In a system of the type described, the

combination with a motor having a field winding of a source of excitation. for the field winding, a reactance connected in series with the field winding of the motor, a resistance connected across the field winding and the reactance during the starting of the motor, a frequencynelay connected across said reaotance and responsive to the frequency of the induced current in the field winding and a switch operable by said frequency rela to supply excitation current to the field win ing when the frequency of the induced current has decreased to a predetermined value, said switch having means, for opening the circuit of the resistance connected to the field winding and the reactance without disconnecting, the reactance from the field circuit.

18, The combination with a synchronous motor, of means comprising electro-responresponsive relay to be included in the field circuit of said motor and a react-ance to be included in the field circuit of said motor.

19. The combination with a synchronous motor, of means comprising electro-responsive switches for establishing starting and running power connections therefor, control means for said switches insuring establishment of said starting connections prior to establishment of said running connections and establishment of running connections upon interruption of starting connect-ions, said means including a normally closed electroresponsive relay to be included in the field circuit of said motor and a react-ance to be included in the field: circuit of said motor to render said rela responsive to a given voltage Which is a unction of the speed of said motor,

20. The combination with a synchronous motor, of means comprising electro-respousive switches for establishing reduced voltage armature connections for starting and full voltage armature connections for running, an electro-responsive switch for connecting the motor field to a source-of direct'current, and control means for the aforesaid switches in eluding a plurality of electro-inagnetic: timing relays included in the field'circuit of said motor during starting and responsive to the slip of the motor, one of said relays controlling said first mentioned switches and the other controlling said last mentioned switch. 21. The combination with a synchronous motor, of means com rising electro-responsive switches for establishing reduced voltage armature connections for starting and full voltage armature connections for runmng, an electro-responsive switch for con; necting the motor field to a. source of direct current,and control means for the aforesaid switches including a plurality of electromagnetic timing relays included in the field circuit of motor during starting and subjected to voltage which is a function of the speed of said motor, one of said relays controlling said first mentioned switches and the other controlling said last mentioned switch.

22. The combination with a synchronous motor, of "means comprising electro-responmien sive switches for establishing reduced volt- 1 age armature connections for starting and high voltage armature connections for running, an elcctm-rcsponsive switch for connecting the motor field to a source of-direct current, a reactancenormally included in the field circuit of said motor by said latter switch and control means for said switches including a plurality of clectro-magnetic relays each having its operating winding connected in shunt with said reactance, one of said relays insuring establishment of said running connections and interruption of said starting connections upon a given speed of said motor and the other insuring closure of said field switch when the speed of said motor approaches synchronism.

23. In a motor control system, the combi:

'nation with an alternating current motorhaving a ficldcircuit that is energized by the motor when the latter operates below synchronous speed and means for establishing starting and running primary connections for said motor, of means for controlling the establishing of said running connection in accordance with the value of the current traversing said fieldcircuit. V

24. The starting system for synchronous motors, comprising the combination with a motor of means including a switch for applying reduced voltage to the armature and means normally connected to the main field winding at all times and exclusively responsive to the induced current in the main field winding for automatically applying 1 full voltage to the armature after the motor has attained a predetermined speed.

25. In a motor control system, the comb ination wlth a motor having a primary circuit and an exciting clrcult and a source of en-- ergy, of means for preventing the connection of sald sourceto said primary circuit to apply normal voltage thereto when the current.

traversing a portion of said exciting circuit exceeds a predetermined value.

26. In a motor control system, the COlTlblnation with an alternating current motor having a field circuit that is energizedby the motor when the latter operates below synchronous speed and means for establishing starting and running primary connections forsaid motor, of meansfoperable only while the starting connections are maintained for controlling the establishing of said running connection in accordance with the value of the current transversing said field circuit.

27. In a motor control system, the combination with a synchronous motor haying a field magnet winding and an armature wind ing, and switching means for establishing starting and running connections for said,

armature winding, of means comprising an r electro-magnetic switch that is operable only when the current traversing a coil thereof is below a predetermined value for successively duced in the fie nections, and the opemn of said starting connections and the establishing of said running connections when the alternating current traversing said field-magnet winding falls below a predetermined value.

28. In a motor control system, the combination with a synchronous motor having a field magnet winding, of means for controlling the establishing of starting and running primary connections therefor, said means comprising a switch embodying electromagnetic means forpreventing the closing of said switch so long asthe current traversing said winding exceeds a predetermined value whilethe starting connections are maintained.

- efiecting the establishing of said starting coni 29. In a system of electrical distribution, a

source of alternating current, a s ehronous dynamo electric machine adapte to be connected-to said source, switching-means for controlling the connection of said machine to said source, and means responsive to the slip f uency of said machine for controlling sai switching means, the means responsive to the sliptfrequcncy of the machine being connected in a closed circuit at all times.

30. The starting system for synchronous I motors, comprising the combination with a motor of means including a switch for apply ingreduced voltage to the armature, and

means normally connectedto'the main field winding at all times and exclusively responsiveto'the frequency of the induced current in the main field winding for automatically applying full voltage to the armature after 9 the motor has attained a predetermined speed. 31. A starting system for synchronous motors, com rising the combination with a motor of. a ouble throw line switch having one set of terminals connected directly to the motor, a source of reduced voltage connected to another set of terminals of said switch and to said motor, means for closingsaid switch to connect the line to the source of reduced voltage whereby reduced voltage is applied to t e motor, and means nor-mall connected to a he main field wind ing of t 0 motor at all times and exclusively ponsive to current induced inthe main- .field winding, for automaticallyweversing said line switch, whereby full voltage plied to the motor. P I v '32. A starting system for synchronous motors, comprising the combination with a motorof a double throw line switch having one set of terminals connected directly tothe mo tor, a source of reduced voltage connected to another set of terminals ofsaid-switch and to said motor, means for closing said switch to connect the line: tothe source of reduced voltage whereby reduced woltage is applied is aptimes. and directly responsive c rrentind winding, or auto to the motor, means normally connected to the main field'winding of the motor at all mat-ically reversing said line switch, whereby full line voltage is applied to the motor,and

means for automatically opening said line switch when said reversing means is inopcratire. Y

In means for starting a synchronous motor the combination with a motor of a two-- way line switch, electromagnetic means for closing said switch in one direction, a second electromagnetic means for closing said main line switch in the opposite direction, means line switch, an adjustable transformer, electromagnetic means for closing the switch in one direction, a second electromagnetic means for closing the switch in the opposite direction,& push button, means controlled by said push button for energizing said first named electromagnetic means, an electrical circuit connecting the motor to be started to a low voltage ta on said transformer when said switch is t rown in its first named position, means controlled by the internal electrical condition of the field winding of the motor to bestarted for throwing said switch to its second named position, a source of field excitation current, means for :11)-

I plying said field excitation current to said eld winding, said last named means being controlled by means whose operations are determined by the internal electrical condition of the field winding. I

35. In a system of the type described, the combination with a motor having, an armature and a field winding of means for applying voltage to the armature, a transformer connected in the field circuit, a frequency relay having a magnetizing coil' connected across the secondary winding of the transformer and a field switch adapted to be closed, by said relay when the frequency of the induced current in the field windingfhas decreased to a predetermined value, the saidtransformer being connected in the-field circuit at all times. Y

36. In a system of the type described, the combination with a motoraving an armature'and, a field winding, of meansfor ap-. plyingvoltage to thearmature, a transformer aving its primary winding connected in series with the fi'eld'winding of the motor, a resistance connectedacross the field windthe internal elecing and the primary winding of the trans former during the starting of the motor, a

frequenc relay connected across the secondary win ing of said. transformer and responsive to the frequency of the induced current in the field winding, and a switch controlled by said frequency relay to supply exitation current to the field winding when the frequency of the induced current has decreased to a predetermined. value, said switch having means for opening the circuit of the resistance connected to the field winding and the primary winding of the transformer without disconnecting the transformer from the-field-circuit. v

' 37. The combination with a synchronous electric motor having a primary winding and a field ma net winding, of a circuit ineluding said field magnet winding and means v inductively relatedto said circuit for controlling the circuit of said primary windmg.

38. The combination with a synchronous alternating current motor havin a primary winding and a field magnet win ing, of electromagnetic means for controlling the circuit connections of said primary winding in accordance with current conditions in the circuitof said field magnet winding, said means comprising a relay having a coil in circuit with said windingand -a second coil inductively related to the first named coil.

39. In a motor control system, the combination with a synchronous motor having a field magnet winding, of means for controlling the establishing-cf starting and running primary connections therefor, said means comprising a switch embodying a closing coil and a lockout coil that is energized in accordance with the value of the current traversing said windin said lockout coil being efiectively energize only while the starting connections are'maintained.

40. In a motor starter, the combination with a synchronous motor having a field magnet winding, and startin connections for said motor, of a switch controlled in accordance with the value of the current traversing said winding for controlling the circuit of said winding, a switch for efiecting the transfer from starting con- Motions :to running connections and a relay' having an actuating coil in circuit with said and running winding for controlling the second named switch. a

'41. Ina motor control system, the. coni'bi: nation'with a synchronous motor having a field magnet winding that is self-excited Vwhen the motor operates below synchronous speed, separate means for energizing said,

winding andmeans for applying voltages of different values to said motor for starting and for normal operation, of means'for controlling the value of the voltage-applied to said motor and the connection of said'wind ing to said energizing means in accordance with the value of the current traversing said winding.

42. In a motor control system, the combination with an alternating current motor having a field magnet winding and switching mechanism for establishing main starting and running connections for said motor, of means for energizing said winding during normal operation of said motor, and auto matic means for effecting the establishing of said running connections and the connection of said'winding to said energizing means when the current traversing said winding during the starting operation falls below a predetermined value.

43. In a system of electrical distribution, a source of alternating current, a synchronous dynamo electric machine connected to said source, switching means for controlling the connection of said machine to said source, and means res onsive to the slip fre uency of said machine or controlling the excitation of said machine and the connection of said machine to said source. V 44. In a motor control system, the combination with a motor,a field circuit therefor and means for ener izing said circuit, of a source of energy at ow voltage for starting.

said motor and a source of energy at high voltage for normally supplying said motor, and means for preventing the connection of said energizing means to said field circuit and of said motor to said source of energy at high voltage when the current traversing a portion of said field circuit exceeds a predetermined value.

45. In a motor control system, the combination with an alternating current motor having a field magnet winding and switching mechanism for establishing main starting and running connections for said motor, of means for energizing said winding during normal operation of said motor, and automatic means for eifecting the establishing of said running connections and the connection of said windingto said energizing means when the current traversing said wmding durin the starting operation falls below a pre etermined value, said automatic means. comprising a switch having a coil-that is in circuit with said field magnet winding at all times. 7

46. In a motor control system, the combination with an alternating current motor having a field magnet winding and switching mechanism for establishing main starting and running connections for said motor, of, means for energizing said winding during normal operation of said motor, and automatic meansforeffecting the establishing of said running connections and the connection of said winding to said energizing means when the current traversing said winding during the starting operation falls below a predetermined value, said automatic means comprisinga switch having a closing coil and a. lockout coil that is in circuit with said field magnet winding at all times.

47 In a motor control system, thecombi-. nation with a synchronous motor having a field magnet 'winding that is self-excited when the motor operates below synchronous speed, separate means for energizing said "winding and means for applying voltages of difierent values to said motor for starting and for normal operation, of means for controlling the value of the voltage applied to said motor and the connection of said wrnd- 1 speed, separate means for energizmg said winding and means for applying voltages of different values to said motor for starting and V for normal operation, of means for controlling the value of the voltage appliedto said motor and the connection of said winding to said energizing means in accordance with the value of the current traversin said winding, said means comprising a switc having a clos ing coil and a lockout coil that retains said switch in open position so long as said winding is self-excited beyond a predetermined degree.

49. In a motor control system, the combination with a synchronous motor having a field magnet winding that is self-excited when the motor operates below synchronous speed, separate means for energizing said winding and means for applying voltages of diflt'erent values to said motor for starting and for normal operation, of means for controlling the value of the voltage applied to said motor and the connection of said winding to said energized means in accordance with the electrical condition of said winding.

'50. In combination, a source of alternating current, an alternating current dynamo electric machine having an armature winding and field winding, switching means arranged to connect said armature winding to source whereby a low voltage is impresse thereon, switching means arranged to connect said armature winding to said source whereby a high voltage is impressed thereon, means adapted, when operated, to effect the operation of said first menti0nedswitching means, means arranged to supply direct current to said field windin after the operation of said first mentioned switching means, and means responsive to the current through said field winding to effect the operation of said second mentioned switching means.

5L The methodof startin asynchronous motor comprising the app ication of low voltage to the motor and thereafter applying the full voltage of the supply circuit to the motor at a, time when the frequency of the induced field current isa predetermined value and applying the field excitation current to the field winding at a time when the freqluency of the induced field current is a prec etermined value.

52. The method of starting a synchronous motor which consists in accelerating said motor to synchronous speed by applying voltage to its armature winding while its field magnet winding is short-circuited, opening the circuit of said field magnet winding when the current traversing it is substantially zero, connecting said field magnet winding to a source of energy and applying voltage to the armature winding.

The method of starting a synchronous motor comprising the application. of low -voltage to the motor and thereafter applying the full voltage of the supply circuit to the motor at a time when the induced field current is a predetermined value and applying the field excitation current to the field winding at a time when the frequency of the induced field current is a predetermined tu valueand at the instant of a predetermined direction of pulsation of the said induced -field current.

54. The method of starting asynchronous motor comprising the application of a low voltage thereto, thereafter applying the full voltage of the supply circuit to the motor at a timewhen the frequency of'the induced field current is a predetermined value and applying the excitation current to the-field winding in such a direction and at such a time as to bring the motor into synchronism.

55. The method of starting a synchronous motor which consists in supplying the motor with a reduced voltage and after the motor has attained a (.OIlSltlGl'flblG percentage of synchronous speed and the frequency of the induced field current has dropped to a predetermined rate, applying the -full voltage of the supply circuit to the motor and when the motor has attained substantially synchronous speed and the frequency of the induced.

field current is low, applying the field excitation current to the field Winding at such an instant with respect to the direction of pulsation of the induced field current that the field excitation current will tend to at once bring the motor into synchronism.

In testimony whereof I aflix my signa- CHARLES TRUMAN HIBBARD. 

